dts

1.Here is my problem I have to import the text file into a destination table using dts, but before doing that
I have to check the condition whether the composite key of source file matches with the composite key of destination
text file, meanwhile i have imported the textfile into a staging table. now i am little confused how to compare the composite
keys and take only valid data rejecting all other data. I will be highly thankful if someone can give me 4 line of
code to compare the composite key. I am little confused also as the destination table doesnt have any data so what is gonna be compared
just the key format.Plz help.